Dxers Unlimited’s mid week edition for Tuesday 11 September 2018

Hola amigos…. more reasons for the very poor propagation conditions on the MF and HF bands. Geomagnetic conditions have reached moderate storm levels on a planetary level (NOAA Kp 6 for the 6-9UT period today, 11 September 2018). The storm is due to the enhanced solar wind parameters associated with a coronal hole high speed stream, while the solar wind speed gradually increased from 370 km/s at noon 10 September to values near 610 km/s at 10UT today.

Now more radio hobby related information useful for planning your on the air activities….

DXCC COUNTRY/ENTITY REPORT: According to the AR-Cluster Network for the week of Sunday, 2nd/September, through Sunday, 9th/September  they were 206 DX countries or entities on the air on the monitored amateur bands.

I am Arnaldo, Arnie, Coro your host here at the middle of the week edition of Dxers Unlimited. Now our next news item… A number of hand held FM transceivers capable of transmitting on frequencies beyond the 2 meters and 70 centimeters band are being banned by several frequency management authorities around the world. The usually very low cost dual band FM handie talkies are considered a menace because they can easily be reprogrammed to operate on the public services frequencies. Banning those radios is achieved by placing them in black lists kept by Customs in the countries were they are no longer allowed to be imported.

QSL on the air… QSL on the air to Dxers Unlimited’s listeners that have asked to keep the HF bands propagation updates at the end of the show on every program…. Don’t worry, from now on whenever possible  Arnie Coro’s HF plus low band VHF propagation update will be on the air at the end of the show.

Next news item : Sponsored by the International Telecommunications Union, ITU, the specialized oldest United Nations agency, a worldwide research project that is measuring the radio frequency spectrum noise levels will provide valuable information about this severe problem that has a negative impact on the use of radio telecommunications systems that are vital in today’s world….

By the way some of the worst radio broadband noise levels measured at several megalopolis, like Mexico City, New York, London, Shanghai, Tokio, Moscow and Paris are showing that the AM broadcast band services are becomming useless at the present transmitting stations power levels… The actual effective service area originally planned for many AM broadcast stations since 1959 have proven to be practically useless due to the poor signal to noise ratios prevaling on the 530 to 1700 kiloHertz frequency range….

Hurricane Florence now in an almost fixed track is going to impact the US East Coast as a category 4 or even category 5 storm, the most powerful to reach that part of the continental USA in more than 60 years… Amateur radio operators located in the affected areas as well as others around the first skip HF coverage area are already deploying their emergency communications stations.  It is expected that the record breaking winds will produce considerable damage to the telecommunications and broadcasting facilities. As it happened last year in Texas, the cellphones networks went down even before the full blast of hurricane Harvey had hit the area, making the use of amateur radio emergency systems essential for responding to life saving operations requiring air evacuations from flooded isolated areas…

Number 94 is here… Yes amigos, the number 94 way of enjoying our spare time by means of our radio and  TV hobby is here: It is known as amateur digital television, capable of high definition transmissions. For   delivery   of   TV   signals,   there   are   several methods   in   use,   including:     cable   (C), satellite (S), terrestrial (T), internet streaming (www), DVD, etc.    Each delivery system has   it’s   own   advantages   and   disadvantages.      As   a result,   different   digital   encoding mechanisms are used for each method.     The cable, satellite and terrestrial all use RF carriers, while satellite and terrestrial are truly over the air rf paths.   As radio amateurs, we use over the air rf transmission paths.

In the early days of DTV (early 2000s), some DTV hams were experimenting with using satellite TV equipment, mainly due to the low cost (? $25) of free-to-air (FTA) satellite, L-band (1-2GHz) receivers.   Their work was primarily   on   the 23cm   (1.2GHz)   band.   Other   early   adopter  DTV  hams experimented using cable TV equipment for the same low cost reasons. The   normal   amateur   radio   environment   is   really   the over   the   air,  Terrestrial,   rf transmission   with   radio waves   being   transmitted   horizontally   over   the surface   of   the earth.   The major issues encountered with such radio waves is the presence of multi-path, RFI and weak signals. Multi-path refers to multiple rf signals bouncing off of various reflectors, such as hills, buildings, etc. and arriving at the receiving antenna with various time delays.   In the days of analog TV, this was readily evidenced by the presence of “ghost” signals on the TV screen. DTV  transmission   in   a   cable  TV  environment   is   rf transmission   in   an   almost   perfect environment.   It is almost a perfect, echo free environment due to the efforts made to maintain very low VSWR in the cable TV system.   Signal strengths can also be kept up to relatively high levels.   Thus the digital modulation method for cable TV does not need to make many corrections for it’s good environment.

DTV   transmission   from   broadcast   TV   satellites   is again   in   a   relatively   clean   rf environment.   Because of the high gain and directivity of the receive antennas, there is essentially no multi-path to contend with from satellites.  The main issue for satellite rf signals is very low signal strength at the receive antennas. Terrestrial rf transmission is the worst possible rf environment.   It must deal with multi-path, RFI, and weak signals and still deliver a perfect DTV picture.

Here in Cuba our national television uses the highly efficient DTMB’T that has proven to be more reliable than the ATSC systems variants used in the USA. So far Cuban radio amateurs have used analog Television transmissions using several slow scan TV modes that proved to be very effective sending still photos of hurricane affected areas to the Civil Defense command posts using both 2 meters FM and HF single side band transmissions.

This is Radio Havana Cuba, the name of the show is Dxers Unlimited. I am your host Arnaldo, Arnie Coro and here is our next radio hobby related item for today… it is about the really amazing results achieved by minimalist amateur radio stations, using minimum parts counts receivers and transmitters…

Starting with dual triodes tubes in a glass envolope the regenerative receiver was designed to work on the 40 meters amateur band, using high impedance headphones . The first triode is the detector and the second one works as an audio amplifier… The radio tunes from 7000 to 7150 kiloHertz only. It has good sensitivity and uses very common electronic parts that you can find by recycling equipment…

It uses a low voltage power supply that is also easy to build… The transmitter first option uses quartz crystal control and a single power tetrode or pentode vacuum tube, that when fed from a voltage doubler power supply will easily provide between two and five watts into the simple half wave coaxial fed dipole antenna. When a local amateur that is a QRP low power radio enthusiast saw the minimalist station he said, and I agreed with him, that it is a simplified version of the famous World War II Paraset !!! He took the circuit diagrams and photos to duplicate the set.

And now at the end of the show…. Arnie Coro’s HF propagation update…. Zero sunspots … a blank solar disc with very low solar activity …AND A GEOMAGNETIC STORM IN PROGRESS: As predicted, a moderately strong G2-class geomagnetic storm was underway on Sept. 11th as a stream of high-speed solar wind buffets Earth’s magnetic field. This morning in Alaska, “amazing auroras covered all of the sky,” reports Ayumi Bakken from just outside Fairbanks.

Send your signal reports and comments about this program to inforhc at enet dot cu or Via Air Mail to Arnie Coro , Radio Havana Cuba, Havana, Cuba.


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